1. Field of the Invention
The invention relates to a process for preparing organosilicon compounds which contain at least one H.sub.2 C.dbd.CH--Si-group, by reacting an organosilicon compound which contains at least one H--Si-group with acetylene in a gas/liquid phase in the presence of at least one addition catalyst and extracting the organosilicon compound which contains at least one H.sub.2 C=CH--Si-group from the reaction mixture.
2. Discussion of the Background
It is known that vinylhalosilanes are obtained by acetylene being reacted, in the presence of a platinum catalyst, with a halosilane which contains 1 or 2 hydrogen atoms bound to the silicon and may or may not contain an inert univalent organic radical, if the reaction is carried out by heating, i.e. in a temperature range of from 80 to 120.degree. C., in a liquid diluent and under atmospheric pressure. Thus German Patent No. 12 32 580 discloses that this process can be carried out discontinuously or continuously and that preferably only a slight excess of acetylene is used, based on the stoichiometric amount of the halosilane employed containing H--Si-bonds. Via this process, according to the examples of German Patent No. 12 32 580, product yields are achieved from around 80% up to 91%.
DE-A 21 31 742 teaches a process for the preparation of alkenylsilanes, by the addition of acetylene, which may or may not be substituted, to silanes being carried out in disilylethanes at from 120 to 220.degree. C. and gauge pressures from 0.1 to 5.0 atmospheres, and the alkenylsilane obtained is removed continuously, as it is formed, and only as a gas from the reaction chamber. The preferred catalyst system used in this case comprises the reaction products of chloroplatinic(IV) acid with ketones.
The abovementioned processes have in common thy the addition of an acetylene to a silane which contains at least one H--Si-group takes place in tank reactors or reaction towers, one of the objectives having been to ensure a maximum mass transfer area and adequate residence times. Installations of these types are generally cost-intensive.
In more recent studies regarding the hydrosilylation of acetylene and trichlorosilane, immobilized platinum complex catalysts are used, yields of 80% being achieved with a selectivity of 100% for vinyl trichlolosilane; Catalysis of hydrosilylation, Part XXII, Applied Organometallic Chemistry Vol 7 (1993), p. 207-212!. However, the preparation of such catalysts is comparatively complicated.
Another important economic aspect of the addition reactions in said processes involves the losses of acetylene which occur owing to unreacted amounts of acetylene, which as a rule are then removed from the process together with the waste gas and, for example, undergo thermal recycling in the form of a combustion plant.
It was an object of the present invention to provide a process via which organosilicon compounds which contain at least one H.sub.2 C.dbd.CH--Si-group can be prepared in a simple and economic way.
This object is achieved according to the invention in accordance with what is specified in the claims.